A known driving force distribution/transmission device for a vehicle and the like is a differential unit having two adjustable clutches.
This differential unit transmits an input driving force to a gear output member through meshing hypoid gears that are examples of two gears arranged on different axes. The gear output member transfers and outputs the driving force through the engagement adjustment of the two adjustable clutches.
This differential unit is arranged in, for example, a secondary drive line of a four-wheel-drive vehicle, to distribute and output a driving force from an engine to left and right wheels through the output adjustment of the driving force conducted by the two adjustable clutches.
Such a differential unit, however, connects a lubrication space of the hypoid gears to a lubrication space of the adjustable clutches, to raise a risk of biasing lubrication oil toward one of the adjustable clutches when the vehicle makes a turn, causing insufficient lubrication on sliding parts such as the other adjustable clutch, and thereby deteriorating reliability.
Patent Literature 1; Japanese Unexamined Patent Application Publication No. H09-328021